Taken in the Octagon Room of Christopher Wren's Flamsteed House, at the Royal Observatory, Greenwich (UK). This room is where the original observatory was housed and where Flamsteed worked and stored his instruments for almost forty years. The observatory is now a part of the National Maritime Museum, and houses an extraordinary collection of historic chronological and astronomical instruments (including John Harrison's chronometer).
This image is of one of the clocks embedded in the walls on either side of the room's entrance. It is a kind of double-image, with the room's tall windows reflected in the glass cover of the clock's display case.